The most common and most likely answer to this crossword clue is the 7 letter word NULLIFY
I've seen this crossword clue in Independent
N
U
L
L
I
F
Y
More clues leading to the result NULLIFY
- Put an end to fun frolicking with Lily
- Some on reflection uselessly fill unfillable void
- Cancel note I fully disputed
- Revoke in full for a change? Yes
- Veto takes over year to satisfy one abroad
- Opposite of fun getting poorly; happy ending is void
- Bring to an end riotous fun with Lily
- Carefully fill unchecked boxes up to cancel
- Make invalid somehow fly in? Extremely unusual
- Veto fully in order
Buddy explains!

The straight part
We know that "Cancel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cancel = nullify.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does NULLIFY mean?
NULLIFY verb- To make legally invalid.
- To prevent from happening.
- To make of no use or value; to cancel out.